JP7479902B2 - Refrigerant charging method and refrigerant charging system for cold heat supply system - Google Patents

Description

The present invention relates to a refrigerant charging method and a refrigerant charging system for a cold heat supply system.

Conventionally, for example in the food sections of supermarkets, refrigerated showcases have been installed to display refrigerated foods. These refrigerated showcases are generally equipped with an indoor unit that has an evaporator, and although this varies depending on the food being displayed, for example in the case of meat and fresh fish, the temperature inside the refrigerated showcase is controlled to maintain a temperature range of -2°C to 2°C. In many cases, this type of control involves ON-OFF control of the compressor according to the compressor inlet pressure setting.

Regarding large-scale retail stores such as supermarkets, local governments establish installation guidelines based on the Large-Scale Retail Store Location Law, which also regulate energy conservation. From this perspective, refrigerated showcases also have energy-saving features in place to supplement the simple refrigeration cycle cold heat supply system.

In this regard, a cold heat supply system equipped with a subcooling device that cools the refrigerant from the condenser using the latent heat of vaporization of water is used in such refrigerated showcases.

This subcooling device sprays water onto a refrigerant pipe through which a cooled, high-pressure refrigerant flows from a condenser installed in an outdoor unit, and the temperature of the refrigerant is further lowered (so-called supercooling) by the latent heat of evaporation of the water at that time. The cooled liquid refrigerant is then sent to an evaporator installed in a refrigerated showcase, and cold heat from the evaporator is supplied to the interior of the refrigerator. This can increase energy conservation effects. In this case, it is known that in a subcooling device with such a configuration, air bubbles and the like are mixed into the refrigerant supplied to the subcooling device, and sufficient energy conservation effects cannot be obtained in a gas-liquid two-phase state.

Therefore, in a cold energy supply system having such a subcooling device, it is necessary that the refrigerant upstream of the subcooling device is only in the liquid phase. Also, it is considered effective to fill the system with a larger amount of refrigerant than usual so that sufficient energy saving effects can be obtained, especially in the summer.

However, determining how much refrigerant to add is an extremely difficult problem, and the inventors have confirmed that simply adding more refrigerant can actually cause the compressor to shut down due to a high-pressure cut, especially in the summer.

As a method of injecting refrigerant into a refrigeration cycle, as described in Patent Document 1, a refrigerant injection method has been proposed in which the refrigerant on the expansion valve inlet side in a subcooling cycle having a degree of subcooling is detected as being in a gas-liquid two-phase state or a liquid state, and when the refrigerant on the expansion valve inlet side is in a gas-liquid two-phase state, refrigerant is sealed into the subcooling cycle until the refrigerant on the expansion valve inlet side changes to a liquid phase, and when the refrigerant on the expansion valve inlet side is in a liquid phase state, the refrigerant in the subcooling cycle is discharged until the refrigerant on the expansion valve inlet side changes to a gas-liquid two-phase state, and then a predetermined amount of refrigerant corresponding to a predetermined degree of subcooling is sealed into the subcooling cycle.

Japanese Patent Application Laid-Open No. 6-101940

However, the technology described in Patent Document 1 does not disclose any solution as to how much additional refrigerant should be charged, and the issue of how much additional refrigerant should be charged to a cold energy supply system that has a subcooling device in order to achieve the energy-saving effects of the subcooling device remains an issue to be resolved.

The present invention was made in consideration of these points, and aims to fill an appropriate amount of refrigerant in a cold heat supply system equipped with a subcooling device between a condenser installed on the outdoor side and an evaporator on the indoor side, which cools the refrigerant from the condenser using the latent heat of evaporation of water.

To achieve the above object, the present invention provides a method for filling a refrigerant in a cold energy supply system that is provided with a subcooling device between a condenser installed on the outdoor side and an evaporator on the indoor side, which performs a cooling process on the refrigerant from the condenser, and is configured to send the refrigerant cooled by the subcooling device to the evaporator. The method is characterized in that a refrigerant state confirmation means is provided in the refrigerant piping between the condenser and the subcooling device, the refrigerant is injected in a space in which the condenser is placed under a specified atmosphere, the subcooling device is stopped, and the compressor is operated, and the refrigerant is injected until the refrigerant confirmed by the refrigerant state confirmation means is only in the liquid phase, and the pressure of the refrigerant on the outlet side of the compressor reaches the pressure value immediately before the compressor was stopped.

According to the present invention, with the space in which the condenser is placed under a predetermined atmosphere, the subcooling device is stopped, and the compressor is operated, refrigerant is injected until the refrigerant pressure at the outlet side of the compressor reaches the pressure value immediately before the compressor was stopped, so that an appropriate amount of refrigerant can be overfilled, preventing a high pressure cut in summer, for example, which would occur if the refrigerant was simply overfilled by additional filling. Therefore, it is possible to safely operate a cold energy supply system having a subcooling device while enjoying the energy saving effect of the subcooling device.
As the refrigerant state checking means, for example, a commercially available sight glass can be used. Of course, the refrigerant state checking means is not limited to this, and may be anything that can check the phase state of the refrigerant, i.e., whether it is at least in the liquid phase or in the two-phase gas-liquid state.

The specified atmosphere may be the temperature atmosphere of the annual maximum temperature of the area where the cold energy supply system is installed. Here, the area where the cold energy supply system is installed may be, for example, a prefecture, city, ward, town, or village. The annual maximum temperature may be, for example, the annual maximum temperature of the year in which the cold energy supply system is installed or the previous year. It may also be a normal value. Furthermore, the temperature atmosphere may be one of the top 10 maximum temperatures of the area where the cold energy supply system is installed. To be on the safe side, the temperature may be, for example, 3 to 5 degrees Celsius higher than the annual maximum temperature. To more reliably prevent high pressure cuts, it is better to have an even higher temperature atmosphere. It may also be a so-called summer atmosphere.

The temperature of the specified atmosphere may be specifically set to 32°C or higher. It is preferable to set the temperature of the atmosphere to 35°C or higher, and more preferably 38°C or higher.

The specified atmosphere may be the atmosphere in a space formed by surrounding at least the space in which the condenser is placed with a partition material. In other words, the specified atmosphere may be created artificially. Here, surrounding at least the space in which the condenser is placed with a partition material means, for example, surrounding or covering the condenser with a vinyl sheet or panel material to create the specified atmosphere in the space in which the condenser is placed. Since the condenser generates heat, by surrounding it with such a sheet material, it is possible to easily create such a specified atmosphere without applying energy from the outside. Therefore, the present invention can be preferably implemented regardless of the season, whether in a cold region or a warm region. Of course, the space formed by surrounding it with the partition material may be heated with a heater or the like.

The space surrounded by the partition material may be partially openable. In other words, when creating a specified atmosphere, if the temperature exceeds the expected temperature, such atmosphere control is possible by opening a portion of the sheet material. In other words, it is preferable that the space surrounded by the partition material to create a specified atmosphere is partially openable. This makes it possible to more appropriately and easily create a simulated summer atmosphere, for example.

When injecting the refrigerant, it may be injected in a gaseous state from a refrigerant filling port that is usually set on the inlet side of the compressor. When injecting in a gaseous state, the refrigerant is often a mixture of multiple substances, and in order to prevent the composition of the refrigerant from changing during injection, it is preferable to inject it in a liquid state from the downstream side of the condenser. That is, for example, it is good to inject the refrigerant into the refrigerant piping between the condenser and the subcooling device. Also, when a subcooling device is retrofitted to an existing refrigeration cycle system, the construction area can be reduced by injecting it on the condenser side, which is closer to the installation location of the subcooling device.

When injecting the refrigerant until the pressure of the refrigerant in the refrigerant piping reaches the pressure value immediately before the compressor is stopped, for example, a pressure gauge can be monitored and the refrigerant injection can be stopped based on the change in the waveform over time, or quantitatively when the pressure value reaches 85% or more of the stop pressure set for the compressor.

From another viewpoint, the present invention provides a refrigerant charging system in a cold heat supply system including a subcooling device disposed between a condenser provided on the outdoor side and an evaporator on the indoor side for cooling refrigerant from the condenser, and configured to send refrigerant whose temperature has been lowered by the subcooling device to the evaporator, the system comprising: a refrigerant state checking means for checking a state of refrigerant in refrigerant piping between the condenser and the subcooling device; a refrigerant injection device for injecting refrigerant into the refrigerant piping; a pressure detection device for detecting the pressure of refrigerant in the refrigerant piping on the compressor outlet side ; and a control device for controlling the amount of refrigerant injected by the refrigerant injection device so as to inject the refrigerant until the refrigerant state checking means checks that the refrigerant is only in a liquid phase and the pressure detected by the pressure detection device reaches a pressure value immediately before the compressor was stopped .

This refrigerant charging system makes it possible to always charge the refrigerant piping with a specified overcharge amount of refrigerant, regardless of the judgment of individual workers.

In this case, the refrigerant state confirmation means can check whether the refrigerant is only in the liquid phase by, for example, using a sight glass as the refrigerant state confirmation means, capturing an image of the refrigerant phase state visible through the sight glass with an image sensor, and outputting a signal when it detects that there are no bubbles, and controlling the refrigerant based on the signal, for example, on the next pressure value.

As for the control by pressure value, it is proposed to monitor the pressure waveform so that the injection is stopped when the pressure exceeds a predetermined value, and to control the injection to be stopped when a steep rising waveform is detected. If the pressure exceeds an upper limit of a predetermined value, the refrigerant may be appropriately removed to perform fine tuning.
Furthermore, the refrigerant charging system of the cold heat supply system may be configured so that the refrigerant is injected with the subcooling device stopped and the compressor operating.
The refrigerant may be injected into a space in which the condenser is placed under a predetermined atmosphere.
Furthermore, the pressure value immediately before the compressor is stopped may be set to 85% or more of the stop pressure set for the compressor.

According to the present invention, an appropriate overcharge amount of refrigerant can be supplied to the cold heat supply system, thereby enabling the cold heat supply system to be operated safely while enjoying the energy saving effect of the subcooling device.

1 is a schematic diagram of a cooling heat supply system in which a refrigerant charging method according to an embodiment is carried out; 2 is a side view showing a state in which the outdoor unit in the cold heat supply system of FIG. 1 is surrounded by a partition material. 4 is a graph showing changes over time in refrigerant pressure at the inlet and outlet sides of a compressor when the compressor is subjected to high pressure cut. 4 is a graph showing changes over time in refrigerant pressure at the inlet and outlet sides of a compressor when an appropriate refrigerant overcharge amount is used. 1 is a schematic diagram of a cooling heat supply system to which a refrigerant charging system according to an embodiment of the present invention is applied;

The refrigerant charging method according to the embodiment will be described below. FIG. 1 is a schematic diagram of a cold heat supply system 1 in which the refrigerant charging method according to the embodiment is implemented. In this example, the system is configured to supply cold heat to a refrigerated showcase 3 installed in a store 2. Food items 4 to be stored in a refrigerator, such as meat and fresh fish, are displayed in the refrigerated showcase 3.

The cold energy supply system 1 has a compressor 10, a condenser 12 provided in an outdoor unit 11, a solenoid valve 13 that functions as an expansion valve, and an evaporator 14 provided in a refrigerated showcase 3. The outdoor unit 11 is provided with a fan 15, which releases heat generated by the condenser 12 outdoors.

Between the condenser 12 and the evaporator 14, a subcooling device 20 is provided that cools the refrigerant from the condenser 12 using the latent heat of evaporation of water. The subcooling device 20 sprays water from a sprinkler device 24 inside a casing 23 onto a pipe 22 that continues from the refrigerant pipe 16 through which the refrigerant from the condenser 12 flows, and supercools the refrigerant in the pipe 22 using the latent heat of evaporation of the water generated during the spraying process. Water is supplied to the sprinkler device 24 from a water supply pipe 26 by a pump 25. A drain pan 27 is provided below the pipe 22, and collects the sprayed water and discharges it from a drain pipe 28. A fan 29 is provided above the sprinkler device 24, and heat inside the casing 23 is released to the outside.

The refrigerant supercooled by the subcooling device 20 flows through the refrigerant pipe 31 that continues from the pipe 22 and is supplied to the evaporator 14. A solenoid valve 13 is provided on the refrigerant pipe 31, and the refrigerant that has passed through the solenoid valve 13 and has a low temperature is supplied with cold by the evaporator 14 to the refrigerated showcase 3. The low-pressure refrigerant that has passed through the evaporator 14 is sent to the compressor 10 by the refrigerant pipe 32. The high-temperature, high-pressure refrigerant compressed by the compressor 10 flows through the refrigerant pipe 33 and is sent to the condenser 12 of the outdoor unit 11.

As mentioned above, in a cold energy supply system 1 equipped with a subcooling device 20 having such a configuration, it is considered effective to fill the refrigerant with an amount of refrigerant greater than the normal amount in order to properly utilize the performance of the subcooling device 20. However, as mentioned above, it is difficult to determine the amount of additional refrigerant to be filled.

The refrigerant charging method according to the embodiment is carried out, for example, through the following process. First, a sight glass 41, for example, is provided as a refrigerant state checking means in the refrigerant piping 16 between the condenser 12 and the subcooling device 20. The refrigerant piping 16 is also provided with a pressure gauge 42 that detects the pressure inside the piping. Then, the periphery of the outdoor unit 11 having the condenser 12 is surrounded by a partition material 43 to form a closed space S, as shown in FIG. 2.

In this case, in this embodiment, the outdoor unit 11 has a condenser 12, but the compressor 10 is installed separately from the outdoor unit 11. In such a case, the compressor 10 may be enclosed with a partition material 43 so as to include it. In other words, the compressor 10 may be housed in the closed space S. In the case of an outdoor unit equipped with a compressor and a condenser, the outdoor unit is housed in the closed space S. In addition, a subcooling device 20 may be housed in the closed space S, as shown in FIG. 2.

A suitable partition material 43 is, for example, a vinyl sheet, but other sheet materials or panel materials may also be used. A partition material that is easy to assemble and remove is suitable. The closed space S does not need to be an airtight closed space, and it is preferable for there to be appropriate gaps. When forming the closed space S with the partition material 43, it is preferable to have a configuration in which a portion of it can be opened freely. For example, if it is formed of a vinyl sheet, such an open portion can be easily formed by flipping over a portion. In short, it is preferable for the atmosphere in the closed space S to be appropriately released, thereby adjusting the temperature in the closed space S.

The refrigerant injection device 50 and refrigerant extraction device 60 are installed, for example, upstream of the sight glass 41 in the refrigerant piping 16. The refrigerant injection device 50 has an injection pipe 52 with a variable valve 51, which is connected to the refrigerant piping 16. The refrigerant extraction device 60 has an extraction pipe 62 with a variable valve 61, which is connected to the refrigerant piping 16. Note that FIG. 2 simply illustrates the injection pipe 52 and extraction pipe 62 connected to the refrigerant piping 16, but in actual operation, the injection pipe 52 and extraction pipe 62 are connected to dedicated ports (not shown) provided on the refrigerant piping 16.

Next, the specific operation will be described. First, the compressor 10 is operated with the subcooling device 20 stopped. This creates a refrigeration cycle in which the refrigerant flows through the refrigerant pipe 33, the condenser 12, the refrigerant pipe 16, the pipe 22 of the inactive subcooling device 20, the refrigerant pipe 31, the solenoid valve 13, the evaporator 14, the refrigerant pipe 32, and returns to the compressor 10.

In this way, the atmosphere in the closed space S can be made to be a pseudo-summer atmosphere by the heat dissipation from the outdoor unit 11 having the condenser 12. An example of a pseudo-summer atmosphere is an atmosphere in which the temperature in the closed space S is between 38°C and 42°C. Maintaining the atmosphere in the closed space S within such a temperature range can be easily achieved by opening a portion of the partition material 43 as appropriate and releasing the atmosphere in the closed space S to the outside as appropriate, without requiring any energy from the outside.

In this state, refrigerant is injected from the refrigerant injection device 50 into the refrigerant piping 16. At this time, the refrigerant is injected until it reaches a liquid phase as confirmed by the sight glass 41. After that, the refrigerant is further injected until the pressure in the refrigerant piping 16, monitored by the pressure gauge 42, reaches the pressure value just before the compressor 10 stopped.

In other words, when the compressor 10 is operated with the subcooling device 20 stopped and the solenoid valve 13 is controlled to turn ON/OFF so that the refrigerated showcase 3 is at a predetermined temperature, for example, between -2°C and 2°C, when the solenoid valve 13 is OFF (closed), the outlet pressure of the compressor 10 rises, and when the solenoid valve 13 is ON (open), the outlet pressure of the compressor 10 drops. The pressure change at this time is shown in the graph in Figure 3. In the graph, P1 indicates the inlet pressure of the compressor 10, and P2 indicates the outlet pressure of the compressor 10.

However, if the amount of refrigerant filled exceeds the appropriate value, the outlet pressure P2 of the compressor 10 will eventually exceed the stop pressure value (e.g., 4.1 MPa), and the compressor 10 will stop (at 1000 seconds in the graph of Figure 3). This occurs because the amount of refrigerant filled is too large.

Therefore, the charging of the refrigerant is stopped just before the compressor 10 stops. To stop charging the refrigerant when the outlet pressure P2 of the compressor 10 reaches the pressure value just before the compressor stops, for example, such a charging operation can be repeated several times while monitoring the pressure value from the pressure gauge 42, and the value just before the compressor 10 stops can be ascertained, and the injection of the refrigerant can be stopped when the pressure value is reached. If too much refrigerant is charged, the refrigerant is appropriately extracted from the refrigerant extraction device 60 and the charging operation is carried out again.

However, since repeating such work is laborious, it is also possible to monitor the pressure value of the pressure gauge 42 and stop the injection of refrigerant when the pressure value quantitatively reaches, for example, 90% or more of the stop pressure set by the manufacturer of the compressor 10.

Alternatively, the pressure value from the pressure gauge 42 can be monitored over time, and the injection of refrigerant can be stopped if a steeper rising peak than normal occurs.

In this way, the pressure change of the compressor 10 when an appropriate overcharge amount of refrigerant is injected into the refrigerant pipe 16 is as shown in the graph of Figure 4. After filling with an appropriate overcharge amount of refrigerant in this way, the subcooling device 20 is operated and normal cold supply operation is performed, so that even in summer, the compressor 10 will not be cut off from high pressure, and the cold supply system 1 can be operated safely while enjoying the energy-saving effects of the subcooling device 20.

Figure 5 shows an outline of the configuration of a refrigerant charging system that can semi-automatically perform the refrigerant charging method according to the embodiment described above. In the figure, the same reference numerals as those used in the description of the refrigerant charging method according to the embodiment described above indicate the same devices and components, and detailed descriptions of these will be omitted.

In this refrigerant charging system, the control device 70 adjusts the opening and closing and the opening degree of each variable valve 51, 61 of the refrigerant injection device 50 and the refrigerant extraction device 60. The control device 70 is configured to receive a detection signal from an image sensor 71 that checks the phase state of the refrigerant using the sight glass 41. The image sensor 71 is, for example, a CCD camera, and an image signal of the sight glass 41 captured by the CCD camera is output to the control device 70. The control device 70 performs calculations on the input image signal to distinguish between gas phase, gas-liquid two-phase, and liquid phase. The control device 70 also receives a pressure signal from a pressure gauge 42.

Then, when the control device 70 confirms that the refrigerant is in liquid phase based on the image signal input from the image sensor 71 and the pressure signal from the pressure gauge 42 reaches, for example, 90% or more of a predetermined pressure value (for example, a compressor stop pressure value preset by the compressor 10 manufacturer), the control device 70 closes the variable valve 51 to stop the charging of the refrigerant from the refrigerant injection device 50.

In such a case, as described above, the pressure value from the pressure gauge 42 can be monitored over time, and if a steeper than normal rising peak occurs, the injection of refrigerant can be stopped. For example, when a steep pressure rise 1000 seconds after the start shown in FIG. 3 is detected, the variable valve 51 can be closed. Of course, it is also possible to fine-tune the amount of refrigerant to be charged by controlling the variable valve 61 of the refrigerant extraction device 60.

With a refrigerant charging system controlled by such a control device 70, it is possible to always charge a specified amount of overcharged refrigerant into the refrigerant piping, regardless of the judgment of individual workers. It is also possible to shorten the time required for this.

The present invention is useful for filling a refrigerant in a cold heat supply system having a subcooling device.

REFERENCE SIGNS LIST 1 refrigeration supply system 2 store 3 refrigerated showcase 4 food 10 compressor 11 outdoor unit 12 condenser 13 solenoid valve 14 evaporator 15, 29 fan 16, 31, 32, 33 refrigerant piping 20 subcooling device 22 piping 23 casing 24 sprinkler device 25 pump 26 water supply pipe 27 drain pan 28 drain pipe 41 sight glass 42 pressure gauge 43 partition material 50 refrigerant injection device 51, 61 variable valve 52 injection pipe 62 withdrawal pipe 70 control device 71 image sensor S closed space

Claims (11)

A method for charging a refrigerant in a cold energy supply system, comprising: a subcooling device disposed between a condenser disposed on the outdoor side and an evaporator disposed on the indoor side, for cooling a refrigerant from the condenser; and a refrigerant whose temperature has been reduced by the subcooling device being sent to the evaporator, comprising the steps of:
a refrigerant state confirmation means is provided in the refrigerant piping between the condenser and the subcooling device;
The refrigerant is injected into the space in which the condenser is placed under a predetermined atmosphere with the subcooling device stopped and the compressor operated.
a refrigerant supplying means for supplying the refrigerant to the compressor from the outlet side of the compressor; a pressure of the refrigerant at the outlet side of the compressor reaching a pressure value immediately before the compressor is stopped; The refrigerant charging method for a cold energy supply system according to claim 1, characterized in that the specified atmosphere is the temperature atmosphere of the highest annual temperature in the area in which the cold energy supply system is installed. The refrigerant charging method for a cold energy supply system according to claim 1, characterized in that the specified atmosphere is an atmosphere with a temperature of 32°C or higher. The refrigerant charging method for a cold energy supply system according to any one of claims 1 to 3, characterized in that the specified atmosphere is the atmosphere within a space formed by surrounding at least the space in which the condenser is placed with a partition material. The refrigerant charging method for a cold heat supply system according to claim 4, characterized in that a portion of the space formed by the partition material can be freely opened. A refrigerant charging method for a cold energy supply system according to any one of claims 1 to 5, characterized in that refrigerant is injected into the refrigerant piping between the condenser and the subcooling device while the compressor is operating. A refrigerant charging method for a cold energy supply system according to any one of claims 1 to 6, characterized in that the pressure value immediately before the compressor is stopped is set to 85% or more of the stop pressure set for the compressor. A refrigerant charging system for a cold energy supply system, comprising a subcooling device between a condenser provided on the outdoor side and an evaporator provided on the indoor side, for cooling a refrigerant from the condenser, and configured to send the refrigerant whose temperature has been reduced by the subcooling device to the evaporator, comprising:
a refrigerant state confirmation means for confirming a refrigerant state in a refrigerant pipe between the condenser and the subcooling device;
A refrigerant injection device that injects a refrigerant into the refrigerant pipe;
a pressure detection device for detecting the pressure of the refrigerant in the refrigerant pipe on the outlet side of the compressor ;
a control device that controls an amount of refrigerant injected by the refrigerant injection device so as to inject the refrigerant until the refrigerant confirmed by the refrigerant state confirmation means is only in a liquid phase and the pressure detected by the pressure detection device reaches a pressure value immediately before the compressor is stopped;
A refrigerant charging system for a cold heat supply system, comprising: 9. The refrigerant charging system of the cold heat supply system according to claim 8, wherein the refrigerant is injected in a state where the subcooling device is stopped and the compressor is operated. 10. The refrigerant charging system of a cold heat supply system according to claim 9, wherein the refrigerant is injected under a predetermined atmosphere in a space in which the condenser is placed. The refrigerant charging system of a cold heat supply system according to any one of claims 8 to 10, characterized in that the pressure value immediately before the compressor is stopped is 85% or more of the stop pressure set for the compressor.

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